Clearing the air to treat hypertension

[Air pollution, noise and hypertension : Partners in crime]

Air pollution and traffic noise are two important environmental risk factors that endanger health in urban societies and often act together as "partners in crime". Although air pollution and noise often co-occur in urban environments, they have typically been studied separately, with numerous studies documenting consistent effects of individual exposure on blood pressure. In the following review article, we examine the epidemiology of air pollution and noise, especially regarding the cardiovascular risk factor arterial hypertension and the underlying pathophysiology. Both environmental stressors have been shown to lead to endothelial dysfunction, oxidative stress, pronounced vascular inflammation, disruption of circadian rhythms and activation of the autonomic nervous system, all of which promote the development of hypertension and cardiovascular diseases. From a societal and political perspective, there is an urgent need to point out the potential dangers of air pollution and traffic noise in the American Heart Association (AHA)/American College of Cardiology (ACC) prevention guidelines and the European Society of Cardiology (ESC) guidelines on prevention. Therefore, an essential goal for the future is to raise awareness of environmental risk factors as important and, in particular, preventable risk factors for cardiovascular diseases.

Particulate Air Pollution and Blood Pressure: Signaling by the Arachidonate Metabolism

BACKGROUND

Short-term exposure to ambient particulate matter (PM) can raise blood pressure, but the underlying mechanisms are unclear. We explored whether arachidonate metabolites serve as biological intermediates in PM-associated prohypertensive changes.

METHODS

This panel study recruited 110 adults aged 50 to 65 years living in Beijing, China. The participants' blood pressure, arterial stiffness, and cardiac and endothelial function were measured up to 7 times. The serum concentrations of arachidonate metabolites were quantified by targeted lipidomics. Ambient concentrations of fine PM (PM2.5), black carbon, and accumulation mode particles were continuously monitored at a station and their associations with the health indicators were evaluated.

RESULTS

Interquartile range increases in 25 to 96-hour-lag exposure to PM2.5, black carbon, and accumulation mode particles were associated with significant increases in systolic blood pressure (brachial: 0.8-3.2 mm Hg; central: 0.7-2.8 mm Hg) and diastolic blood pressure (brachial, 0.5-1.5 mm Hg; central, 0.5-1.6 mm Hg). At least 1 pollutant was associated with increases in augmentation pressure and heart rate and decreases in reactive hyperemia index and ejection time. The serum concentrations of arachidonate were significantly increased by 3.3% to 14.6% in association with PM exposure, which mediated 9% of the PM-associated increases in blood pressure. The levels of eicosanoids from the cytochrome P450, cyclooxygenase, and lipoxygenase pathways changed with PM exposure, and those from the cytochrome pathway significantly mediated the association between PM exposure and blood pressure.

CONCLUSIONS

Short-term exposure to particulate air pollution was associated with a prohypertensive change in adults, which was in part mediated by alteration of arachidonate metabolism.

An updated systematic review and meta-analysis on portable air cleaners and blood pressure: Recommendations for users and manufacturers

Fine particulate matter (PM2.5) air pollution is a leading contributor to the global burden of cardiovascular disease (CVD). One important underlying mechanism is an increase in blood pressure (BP). A growing number of studies have reported a beneficial effect of portable air cleaners (PACs) on systolic and diastolic BP; SBP and DBP. We conducted an updated systematic review and meta-analysis of studies using true versus sham mode filtration reporting the effects on BP. Of 214 articles identified up to February 5, 2023, seventeen (from China, USA, Canada, South Korea and Denmark) enrolling approximately 880 participants (484 female) met the inclusion criteria for meta-analyses. Aside from studies conducted in China, research on PACs and BP has been conducted in relatively low pollution settings. Mean indoor PM2.5 concentrations during the active and sham mode purification were 15.9 and 41.2 µg/m3, respectively. The mean efficiency of PACs against indoor PM2.5 was 59.8 % (ranging from 23 % to 82 %). True mode filtration was associated with a pooled mean difference of - 2.35 mmHg (95 % confidence interval [CI]: - 4.5, - 0.2) and - 0.81 mmHg (95 % CI: - 1.86, 0.24) in SBP and DBP, respectively. After removing the studies with high risk of bias, the magnitude of the pooled benefits on SBP and DBP increased to - 3.62 mmHg (95 % CI: - 6.69, - 0.56) and - 1.35 mmHg (95 % CI: - 2.29, - 0.41), respectively. However, there are several barriers to the use of PACs, specifically in low- and middle-income countries (LMICs), such as the initial purchase cost and filter replacements. There may be several avenues to help overcome these economic burdens and improve cost effectiveness, such as implementing government or other subsidized programs to distribute PACs targeting vulnerable and higher-risk individuals. We propose that environmental health researchers and healthcare providers should be better trained to educate the public regarding the use of PACs to reduce the impacts of PM2.5 on cardiometabolic diseases globally.

Noise and Air Pollution as Risk Factors for Hypertension: Part I-Epidemiology

Traffic noise and air pollution are 2 major environmental health risk factors in urbanized societies that often occur together. Despite cooccurrence in urban settings, noise and air pollution have generally been studied independently, with many studies reporting a consistent effect on blood pressure for individual exposures. In the present reviews, we will discuss the epidemiology of air pollution and noise effects on arterial hypertension and cardiovascular disease (part I) and the underlying pathophysiology (part II). Both environmental stressors have been found to cause endothelial dysfunction, oxidative stress, vascular inflammation, circadian dysfunction, and activation of the autonomic nervous system, thereby facilitating the development of hypertension. We also discuss the effects of interventions, current gaps in knowledge, and future research tasks. From a societal and policy perspective, the health effects of both air pollution and traffic noise are observed well below the current guideline recommendations. To this end, an important goal for the future is to increase the acceptance of environmental risk factors as important modifiable cardiovascular risk factors, given their substantial impact on the burden of cardiovascular disease.

Investigating the association between ambient particulate matter (PM10) exposure and blood pressure values: Results from the link between the Portuguese Health Examination Survey and air quality data

INTRODUCTION AND OBJECTIVES

High blood pressure (BP) remains a major modifiable cardiovascular (CV) risk factor. Several epidemiologic studies have been performed to assess the association between air pollution exposure and this CV risk factor but results remain inconsistent. This study aims to estimate the effect of short-term PM₁₀ exposure (average previous three-day concentration) on diastolic (DBP) and systolic (SBP) blood pressure values of the resident mainland Portuguese population.

METHODS

Our study was based on available DBP and SBP data from 2272 participants from the first Portuguese Health Examination Survey (INSEF, 2015) living within a 30 km radius of at least one air quality monitoring station, with available measurements of particulate matter with an aerodynamic equivalent diameter ≤10 μm (PM₁₀). We used data from the air quality monitoring network of the Portuguese Environment Agency to obtain the individual allocated PM₁₀ concentrations. Generalized linear models were used to assess the effect of PM₁₀ exposure on DBP and SBP values.

RESULTS

No statistically significant association was found between PM₁₀ exposure and both DBP and SBP values (0.42% DBP change per 10 μg/m³ of PM₁₀ increment (95% confidence interval (CI): -0.85; 1.70) and 0.47% SBP change per 10 μg/m³ of PM₁₀ increment (95% CI: -0.86; 1.79)). Results remain unchanged after restricting the analysis to hypertensive or obese participants or changing the PM₁₀ assessment methodology.

CONCLUSIONS

In view of the PM₁₀ levels observed in 2015, our results suggests that exposure to PM₁₀ concentrations have a small or no effect on the blood pressure values. Other air pollutants and mixtures of pollutants that were not included in our study should considered in future studies.

Fine particulate matter and vasoactive 20-hydroxyeicosatetraenoic acid: Insights into the mechanisms of the prohypertensive effects of particulate air pollution

BACKGROUND

Emerging evidence suggests that biological intermediates play an important role in initiating fine particulate matter (PM_2.5)-associated prohypertensive pathways, but sensitive biomarkers for this pathway are lacking.

AIM

To explore whether short-term exposure to PM_2.5 is associated with the concentration of 20-hydroxyeicosatetraenoic acid (20-HETE), a potent vasoactive lipid relevant to the pathophysiology of hypertension.

METHODS

In this longitudinal panel study, we repeatedly (up to seven times) measured the blood concentrations of 20-HETE in 120 adults living in Beijing, China. Ambient exposure metrics included the concentrations of hourly PM_2.5 mass and daily PM_2.5 constituents, including three carbonaceous components, eight water-soluble ions, and 16 trace elements. Linear mixed-effects models were used to examine the associations between the change in the 20-HETE concentration and short-term exposure to ambient PM_2.5 metrics after adjustment for age, sex, body mass index, behavioral exposure, socioeconomic characteristics, and meteorological factors.

RESULTS

The interquartile range (IQR) increase in the 7-15-hour-lag exposure to PM_2.5 (80 μg/m³) was associated significantly with a 5.3% (95% confidence interval [CI], 0.1-10.7%) to 6.5% (95% CI, 1.7-11.6%) increase in the blood concentration of 20-HETE. The magnitude of the association differed by age, sex, prediabetic status, obesity, and hypertensive status, with a significantly greater increase in 20-HETE observed among those with fasting plasma glucose concentrations ≥ 6.1 mmol/L. In addition to the PM_2.5 mass, the 20-HETE concentration was associated consistently with IQR increases in the 1-day lag exposure to organic carbon (5.7%), black carbon (9.5%), nitrate (3.9%), chloride (2.9%), copper (5.5%), zinc (4.7%), barium (4.1%), and lead (6.2%). The organic carbon estimate was robust in the two-pollutant models. Furthermore, increased 20-HETE correlated with elevated blood pressure (BP), although no mediation of 20-HETE on PM_2.5-associated BP change was found.

CONCLUSIONS

The 20-HETE blood concentration increased significantly in response to short-term exposure to ambient PM_2.5, which may be partly responsible for the prohypertensive effects of PM_2.5.

Changes in bioactive lipid mediators in response to short-term exposure to ambient air particulate matter: A targeted lipidomic analysis of oxylipin signaling pathways

BACKGROUND

Exposure to ambient air particulate matter (PM) is a risk factor for cardiometabolic diseases. The knowledge of the underlying mechanisms is still evolving, but systemic inflammation and oxidative stress are central to the ability of PM to induce cardiometabolic effects. Oxylipins derived from polyunsaturated fatty acids (PUFAs) are bioactive lipid mediators that have fundamental roles in the signaling of inflammatory events. However, the associations between oxylipins and short-term exposure to PM in humans are unknown.

METHODS

Using targeted lipidomic analyses, we measured 16 oxylipins derived from lipoxygenase (LOX), cytochrome P450 (CYP), and cyclooxygenase (COX) pathways and their parent PUFAs in serum samples of 110 adults enrolled in a panel study in Beijing, China. Each participant completed 2-7 clinical visits from 2013 to 2015. PM with aerodynamic diameter ≤ 2.5 μm (PM_2.5) and ≤ 0.1 μm (ultrafine particles, UFPs) were continuously monitored at a station. Linear mixed-effects models were applied to examine the associations between changes in lipid mediators and exposure to ambient PM during the preceding 1 to 3 days before the clinical visit.

RESULTS

Serum concentrations of PUFAs, including omega-6 arachidonic acid (ARA) and omega-3 eicosapentaenoic acid (EPA), were significantly increased in association with interquartile range (IQR) increases in PM with different exposure windows (i.e., 1-3 days). Regarding oxylipins, significant PM-associated changes included increases in LOX-derived leukotriene B4 (LTB4), 12(S)-, 15(S)-hydroxyeicosatetraenoic acid (HETE), 12-hydroxyeicosapentaenoic acid (HEPE), and 17-hydroxydocosahexaenoic acid (HDHA); an increase in CYP-derived 5,6-dihydroxyeicosatrienoic acid (DHET); and a decrease in COX-derived prostaglandin E2.

CONCLUSIONS

Short-term exposure to PM was associated with PUFAs and oxylipins derived from LOX, CYP, and COX pathways in humans. Our findings provide mechanistic insight suggesting bioactive oxylipins might be used as biomarkers and have important implications as mediators of PM-associated systemic cardiometabolic effects.